Pump



J. C. FISHER Feb. 28, 1961 PUMP 5 Sheets-Sheet 1 F iled y 1957 Fig. I

sit;

Fig. 2

'LTTT- Fig. 3

R R O E M H E B V F N l C N H O J KENWAY, JENNEY, WITTER & HiLDRETHATTORNEYS Feb. 28, 1961 c F S E 2,972,957

PUMP

Filed May 20, 1957 5 Sheets-Sheet 2 Fig. 4

INVENTOR JOHN C. FISHER KENWAY, JENNEY. WITTER & HILDRETH ATTOR NEYSFeb. 28, 1961 Filed May 20, 1957 Fig. 6

J. C. FISHER PUMP 5 Sheets-Sheet 4 INVENTOR. JOHN C. FISHER KENWAY,'JENNEY. WITTER & HILDRETH ATTORNEYS United States Patent PUMP John C.Fisher, Cambridge, Mass., assignor to 'Am Dyne Trust, a trust ofMassachusetts Filed May 20, 1957, Ser. No. 660,298 7 20 Claims. "(C1,103-76) This invention relates to an improved design of accel eratortube for use in fluid pumps of the types described in my copendingapplication, Serial Nos. 553,015, filed December 14, 1955, now PatentNo. 2,936,713; and 617,- 993, filed October 24, 1956, now Patent No.2,948,225. In pumps of the accelerator-tube type, flexible orsemiflexible tubes must be provided in order to form liquidcarryingtransitions from the moving accelerator tube or tubes, to the stationaryparts of the apparatus; In general, such flexible tubes may be madeeither of metal or of some plastic material. plastics are not suitable.For example, plastics will not withstand high internal temperatures andpressures. Hence, in many cases, metal tubing must be used. Whatever themode of motion may be for the accelerator tube;

its'flexible connections to the stationary parts are subjected tomechanical stresses, due to the relative deflec tion between thestationary and moving ends, which in'-- crease in magnitude as thelength of the flexible connection decreases. of the connectionincreases, the fall of pressure in the internal liquid in the directionof the acceleration of the stream becomes greater. This pressure drop isalways present whenever the liquid in the tube has an acceleration, andby the very nature of the pumping device, the internal liquid must havean alternating acceleration. The net result is that, while theaccelerator tube imparts an acceleration to the liquid opposite to thedirection of internal flow, and thereby creates a rise of pressure inthe direction of flow, the concomitant acceleration of the liquid in theadjacent flexible connections is in the same direction as the flowtherein, and thus causes a drop of pressure in the flow direction whichmust instantaneously detract from the rise of pressure in theaccelerator tube, thus reducing the net alternating pressure diiferencewhich is available for external use beyond the hydraulic rectifyingdevice.

Therefore the designer of a liquid pump of the accelerator-tube type iscon-fronted with conflicting factors: he must make the length of theflexible connecting tubes as short as possible to minimize the internalpressure drop therein, but he must make these same tubes as long aspossible in order to minimize the mechanical stresses in the Walls ofthe tubes. He must also strive to make the effective length of theaccelerator tube as long as possible relative to the total length offlexible tubes and any other static-internal tubes (i.e. tubes lying onthe alternatingflow side of the rectifying device), subject to certainvery important restrictions which are discussed in what follows. Itshould be noted that it is possible, for a given external discharge ofliquid, to reduce the acceleration of the liquid within the flexibletubes by simply increasing their internal cross-sectional area. raisesthe level of mechanical stresses in the walls of these tubes, andhence-is not a solution to the problem. 7 The limitations upon theextent to which the length of an accelerator tube can be increased existbecause no liquid, and no tube which may contain this-liquid, can-However, for many purposes,

On the other hand, as the length.

However, this also sustain internal pressure without an elasticdeformation.

" a mechanical analogy in which a series of'pistons and In simple terms,the liquid is compressible, and the tube expansible,' however slightly.This fact, together with the inertia of the liquid, necessitates afinite time delay in the transmission of pressure changes from one pointto another in a liquid confined within anaccelerator tube. Beyond acertain range of tube lengths, depending upon the properties of theliquid, the properties of the tube material, the dimensions of the tube,and the frequency of alternation of the tube velocity, an increase inthe eifectivelength 'of the accelerator tube no-longer pro duces aproportional increase in the internal pressure rise, other factorsremaining constant. This is so, in general terms, because the liquid inthe tube cannot sustain a tensile stress, and must therefore be pushedby the trailing end of the accelerator tube; but as the length of thetube is increased, alonger time lapse is needed for this push, orpressure impulse, to be propagated elastically along the liquid columntoits other end. When this transit time for pressure-impulses to travelthe length of the tube becomes comparable to the period of thereciprocating motion of the tube, then the liquid within the tube nolonger behaves like a lumped (i.e. perfectly rigid) body whose onlyimportant property is its total mass.

Accordingly, it is the principal object of the invention to provide anaccelerator-tube-type pump designed not only to eliminate, or at leastminimize, the aforementioned difiiculties, but also to operateatrelatively high frequencies, i. e., between 20 and 300 cycles persecond, inyan; efficient and reliable manners Further objects relate'to.features of design and-will .be better, understood from: a considerationof the followingdisclosure and'the ac-v companying drawings .Whichinclude explanatory figures;

and analogies as well as practical embodiments of the invention. H a

In the drawings: 1

Fig. 1 is an axial section through a simple form of accelerator tubehaving a length 8,, and containing an isotropic liquid; 7 7

Fig. 2 is a view similar to Fig. 1, but presenting compression springsreplace the liquid;

Fig. 3 is a view showing an electricalanologue in the form of analternating-current transmission line;

Fig. 4 is a View similar to Fig. 3, but showing an of Fig. 5;

Fig. 7 is a section on the line 7-7 of Fig. 5;

Fig. 8 is a schematic view showing the hydraulic recti- Fig. 10 is aschematic view showing the hydraulic rectifier used with the systemshown in Fig. 9.

In accordance with the present invention my improved pump comprises oneor more accelerator tubes which may be helical or rectilinear and one orboth ends of thetube or'tubes are connected with a hydraulic rectifierop-- erative 'to produce-a unidirectional external liquid flow inresponse to an oscillating fluidflow in the accelerator tube or tubes,as the case may be. The oscillating'fiuid are required, but with astraight tube rectilinear oscillations are employed; For there'asons'hereinafter con- 3 sidered the eifective length of the tube, whetherhelical or rectilinear, should either approximate one-half the sonicwave length within the liquid as confined in the tube at the fundamentaloperating frequency, or any odd-integer multiple of this wave length. Inorder more fully to appreciate the fundamentals underlying the design ofsuch accelerator-tube-type pumps, the considerations hereinafter setforth should be understood,

The design of 'accelerator-tube-type pumps presents a situationinvolving the propagation of sound waves through the liquid'confined inthe tube, and this phenomenon is susceptible to analysis, as shown inthe subsequent discussion. By reference to any textbook on the theory ofsound, it can be verified that the velocity of propagation of sound (orelastic waves) is given by the expression where E =the adiabatic bulkmodulus of compressibility of the liquid, (force)/(length-) m=the massdensity of the liquid;

v =the velocity of sound in an infinite body of the liquid in question.

Note that Equation 1 gives only the sonic velocity in an infinite bodyof the liquid. When the liquid is confined within a metal tube, thevelocity of sound in the axial direction of the tube is less than thatin an infinite body of E D Iii-E;

where E,,=Youngs modulus of elasticity for the tube material,

(force) (length) E =the adiabatic bulk modulus of elasticity of theliquid,

(force) (length) D =the inside diameter of the tube;

fi =the wall thickness of the tube;

v =the sonic velocity in an infinite body of the liquid, as given by Eq.1, (length)/ (time).

It is comparatively simple to derive an expression for the velocity ofelastic waves in a liquid column confined within a tube having a crosssection other than circular, but it is sufficient merely to state herethat, other things being equal, a tube of circular cross section has thehighest sonic velocity within its internal liquid. This is so becausethe perfect symmetry of the circular tube about its axis permits it toexpand only in the barrel-hoop mode, which induces a pure tensile stressin the wall; whereas, a tube of non-circular cross section is subjectedto outward bending of its walls, with the result that the increase ofinternal volume for each increment of internal pressure is greater thanin the case of the circular tube. It should be noted that E is ingeneral a function of both temperature and pressure, but this does notaffect the validity of the analysis.

Consider Fig. 1,.which shows a metal tube 1 of thin wall, long relativeto its diameter, which confines under some pressure, and without voids,a homogeneous, isotropic liquid 2. The tube is closed and sealed at itsends. If this tube is subjected to an alternating rectilinear velocity,V given by v =vv sin 21rft, t =time 1 4 parallel to its axis, and thefrequency of alternation, f, in cycles per unit time, is sufiicientlyhigh that the sonic transit time in the tube is appreciable relative to1/ then we must regard the internal liquid column as a continuousdistribution of mass and compliance (the reciprocal of stiffness). Weshall assume that longitudinal extension and compression of the tubeitself are negligible,

, and that only radial expansion or contraction of the tube is given byEq. 2. This is usually the case with metal tubes of thin wall. It isfurther assumed that the static internal pressure in the confined liquidis sufficiently high so that the symmetrical harmonic increase anddecrease of pressure due to the elastic waves are always of lesseramplitude than this static pressure, and cavitation never occurs.

This continuous distribution of mass and compliance may be associatedentirely with the liquid, for purposes of analysis, and the tube omittedfrom further consideration, it a new bulk modulus of compressibility forthe liquid is defined as follows:

where the various symbols are as previously defined.

Consider the situation as shown in Fig. 2, wherein the actual liquid hasbeen replaced by a large number of identical, pure-mass pistons 3 whichslide without friction inside the perfectly rigid metal tube 1 and areseparated from one another by identical, pure-compliance compressionsprings 4. As the number of pistons and springs is increased, thesituation of Fig. 2. becomes an increasingly better approximation to thesituation of Fig. 1. The mass per unit length of this assembly is whereM =the total mass of the liquid column;

S,=the total length of the liquid column; A ==the internal cross sectionof the tube, or

'll'Di 4 m =the mass density of the liquid, (mass) (volume). Thecompliance per unit length of the assembly in Fig. 2 is 1 l 1 E731 E'wAt(6) where K =the total compressive stiffness of the liquid column inFig. .1 (incl. tube expansion), or (applied force)! (decrease inlength).

The following important observations concerning the assembly shown inFig. 2 should be noted.

(1) Because the metal tube is much less compliant in the axial directionthan is the liquid column or its equiva-v lent array of pistons andsprings, the ends of the tube and of the spring-and-piston column musthave the same velocity at all instants of time;

(2) Because the ends of the tube have identical velocities, and becausethe spring-and-piston column is perfectly symmetrical about its axialcenter, the velocities of any pair of pistons symmetrically disposedrelative to the center must be equal to each other; and

(3) The velocity of any piston lying between either end of the tube andthe center is not equal to the velocity of the tube. end.

*The behavior of the system of Fig. 2 could be determined by directsolution of the basic differential equations for this case, but there isa much simpler method based upon the well known analogy suggested byFirestone, between'mechanical and electrical systems. (See Firestone, F.A., The Mobility Method of Computing the Vibration of Linear Mechanicaland Acoustical Systems: Mechanical-Electrical Ana-logies, Journal ofApplied Physics, volume 9, No. 6, June, 1938.)

In the Firestone Analogy, the following primary variables are analogous:force-electric current, velocityelectro-motive force or potentialdifference, mass-capacitance, and compliance-inductance. By directapplication of the Firestone Analogy to the system of Fig. 2, it can bedemonstrated that its electrical analogue is the electrical transmissionline shown schematically in Fig. 3. It should be noted, with referenceto Fig. 2, that the following facts exist regarding Fig. 3:

(1) The potential dilference between any point of the transmission lineand its ground return is the analogue of the velocity relative to theearth of the corresponding piston in Fig. 2.

(2) The electric current flowing in the transmission line at any pointis the analogue of the total force (pressure times area) transmitted bythe corresponding spring ofFig. 2. (3) The generator end, or sendingend, of the transmission line is connected by a zero-impedance bus barto the receiving end of the line, so that the potential differences ofthese ends relative to ground are always the same.

(4) The series inductance per unit length of the transmission line isthe analogue of the compliance per unit length of Fig. 2.

('5) The shunt capacitance per unit length of line in Fig. 3 is theanalogue of the mass per unit length of Fig. 2.

(6) The plus and minus signs of Fig. 3 indicate that the associatedpotential difference is tov be considered instantaneously positive whenit has that polarity.

(7) The arrows associated with current symbols in Fig. 3 indicate thepositive direction for instantaneous electric currents.

(8) The generator attached to the sending end of the transmission linein Fig. 3 is a source of sinusoidal alternating current and potentialdifference, and corresponds 1 to the mechanism (not shown), whichproduces the sinusoidal tube velocity in Fig. 2.

Because of the bus bar connecting the ends, and the symmetry of thetransmission line about its center, it is clear that points on the linewhich are symmetrically disposed relative to the center must haveidentical currents and potential differences relative to ground. Hencethe transmission line of Fig. 3 is exactly equivalent to thetransmission line of Fig. 4, which has half the length of the line inFig. 3, twice the shunt capacitance per unit length, and half the seriesinductance per unit length. The receiving end of the new line of Fig. 4corresponds to the midpoint of the line in Fig. 3.

Since the theory of lossless electrical transmission lines has beenfirmly established for many years, the equations for the potentialdifference and current at any point on the line of Fig. 4 may be stated,without giving a formal derivation. It is to be noted that losses havebeen neglected in the transmission line because the frictional forces inthe original tube of Fig. 1 are negligibly small equivalent transmissionline of Fig. 4, then the potential difference at the sending end of theline is given by 6. where The electric current at .the sending end ofthe line in Fig. 4 is given by I 7l'fSg where T =the complex algebraicexpression for the sending-end current;

V,=the complex expression for the tial difference; a

Y =the characteristic admittance (a pure real number) of the line inFig. 4;

j=the complex operator which signifies a phase advance of electricaltime degrees.

receiving-end poten- For the significance of complex quantities asapplied to, simple harmonic functions, consult any basic text on thetheory of alternating-current circuits.

In general, the characteristic admittance of a line is defined as thesquare-root of the ratio of shunt capacitance per unit length to seriesinductance per unit length. Hence, for the line in Fig. 4, we have C=the shunt capacitance of the entire line in Fig. 3; I L' =the totalseries inductance of the line of Fig. 3.

where In order to express Y in terms of the mechanical parame v ters ofFigs. 1 and 2, the following fundamental identities which relatemechanical to electrical variables in the Firestone Analogy are used:

where U =the square of the arbitrary transduction constant, U, which isthe ratio of (force)/ (current) or of (potential difference) (velocity).

M, A, and 5, have been previously defined.

w w w i where s,,, B7,, A1, and U are as previouslydefin'ed.

Substitution of the expressions of (10) and (11) into Eq. 9, gives 4 Theelectrical impedance seen by the generator looking into the sending endof the transmission line of Fig. 4

is the ratio of the sending-end potential difference-to the sending-endcurrent:

EFL 13 It Y, tan

I v v,

where Z =the complex expression for the sending-end impedance of thetransmission line of Fig. 4. In view of the fundamental identities ofthe Firestone where F =the complex algebraic expression for thesinusoidally,

varying force exerted by the tube of Fig. 1 or Fig. 2

on either end of the internal column;

v =the complex algebraic expression for the velocity of the tube in Fig.l or Fig. 2.

It follows that Equation 13 expresses the complex ratio of velocity toforce at either end of the tube in Figs. 1 and 2:

Equation 16 leads to a very important conclusion. It is clear that thequantity in the denominator of the right-hand side of (16) is a functionof the frequency, f, since the sonic velocity, v',, and the tube length,8;, are given. Inparticular, if the frequency has the critical value andthe ratio v /F becomes zero. The significance of this, physically, isthat the liquid column inside the tube of Figs. 1 and 2 undergoes aninternal resonance which makes it a vibration absorber, with the ends ofthe liquid column remaining motionless against any finite force whichthe metal tube is capable of exerting.

Under the conditions of Equations 17 and 18, the reactions of the endsof the liquid column against the end walls of the tube are exactly thosewhich would occur ifthe liquid column were replaced by a tight-fittingsolid rod of infinite mass and stiffness.

It should be noted, that when the frequency has the critical value givenby Equation 17, the center of the actual liquid column in Fig. 1 doeshave a finite velocity and zero dynamic alternation of pressure or totalforce, although the ends of the column have zero velocity against afinite alternating force.

The criterionof Equation 17 may be expressed in a slightly different waywhich is more instructive in case the operating frequency, f is fixed,and the length of the tube can be chosen at will. The velocity ofpropagation of sound waves in the liquid column confined within the tubeis related to the frequency of the pressure changes by the equationwhere By means of Equation 19, we may rewrite (17) in the form Thus, theliquid column in the tube becomes a vibration absorber when the totallength of the column is equal to half a sonic wave length at theoperating frequency.

. By means of arr-extension of the" foregoing analysis, it can bedemonstrated that. the following things are true regarding the. tube ofFigs. 1 and 2:

(1) Whenthe total length of the tube is an oddinteger multiple of half asonic wave length at the operating frequency, the liquid column behavesat its ends like a vibration absorber.

(2) When the total length of the tube is any eveninteger multiple ofhalf a sonic wave length at the operating frequency, then the liquidcolumn permits any finite velocity at its ends and will sustain noalternating force or pressure there.

The importance of the foregoing facts in the design of accelerator tubesbecomes evident. If the tube of Fig. 1 is now open at its ends, andconnected to flexible tubes of the same inside diameter, wall thickness,etc., which introduce a change in the stream direction of approximatelyat each end of the tube, then there is produced an accelerator tube ofthe type suitable for pumps like those described in my copendingapplications. The liquid column within the straight accelerator tube nowis no longer pushed by the ends of this tube, but rather is pushed bythe ends of the liquid columns in the adjacent flexible connections. Thebehavior of the inner liquid column is still the same as before,however. Hence if the length of the flexible connections is suflicientlyshort be made to behave like a frictionless piston ofinfinite mass,provided only that the length of the accelerator tube is half a sonicwave length in the liquid column as;

confined by this tube at the fundamental operating frequency, or anyodd-integer multiple of this length. It is not essential that thewaveform of the force applied to the ends of the liquid column be a puresinusoid of the fundamental frequency; any complex waveform of end forceor pressure which contains only odd Fourier harmonics of the basefrequency will cause the liquid column within the accelerator tube tobehave in the same manner. Such Fourier spectra are actually encounteredin many cases of practical application of accelerator-tube pumps.

It should be noted that it is undesirable that the length of theaccelerator tube be any even-integer multiple of half the sonic wavelength, because then the inner liquid column behaves like a liquidpiston of zero effective mass, and the pump becomes inoperable.

In view of the foregoing considerations, the novel features andadvantages of my invention will now be apparent. It provides, within acompact structure, an accelerator tube which has a length exactly equalto half the sonic wave length in the confined liquid at the operatingfrequency, and flexure tubes (flexible extensions) which have shortefiective hydraulic lengths and long effective me-.

chanical lengths. Furthermore, the entire liquid circuit through thisassembly rises continuously from the bottom end to the top end, with nohigh spots, pockets, or domes which can trap air or other gasesinternally. It. is essentially a helix of tube mechanically supportedupon vertical axial extensions of this tube, and driven in a torsionaloscillation by means of two electrodynamic vibra-. tion motorstangentially connected to the helix of tube at opposite ends of adiameter of the structure.

Referring to Figs. 5 to 8, the pump shown therein is designed to operatein conjunction with two other identical units at frequencies betweenapproximately 20 and 300 cycles per second. Each unit is rigidlysupported in a suitable frame (not shown) by upper and lower flangefittings 1 and 2. The upper flange 1 is welded or otherwise suitablyconnected with the upper end of a rigid metal outer tube 4, the lowerend of which is connected by a circular ring 5 of T-shape cross sectionwith the lower end of an intermediate rigid metal tube 6. The

upper end ofthe intermediate tube is connected by another circular ring8 of-T-shape cross section with a rigid metal inner tube 10, and thelower end of the inner tube is connected to a heavy-wall pipe orcoupling 12.

In a similar manner the lower flange 2 is connected with an inner tube14 which is connected by ring 15 to an intermediate tube 16 and thelatter is connected by a ring 18 with an outer tube 20. The upper end ofthe outer tube is connected with a heavy-wall pipe or coupling 22corresponding to the coupling 12. The assemblies 4 to 10 and 14 to 20 toprovide telescopic torsion tubes having an effective mechanical(twisted) length of approximately three times that of any individualconstituent tube.

The lower end of the upper coupling 12 and the upper end of the lowercoupling 22 are provided with flanged metal plugs 24 and 25 (Fig. 7)which fit a hollow central hub 26, thus providing a rigid connectionbetween the telescopic-torsion-tube assemblies. The upper end of theplug 24 and the lower end of the plug 25 are truncated at a 45 angle andopposite their truncated portions the couplings 12 and 22 are providedwith circular openings which receive the upper and lower extensions 28and 30 of a helical coil 32 of metal tubing of circular. cross section,it being understood that the parts are welded, brazed or otherwisesuitably secured to provide leakproof joints. The helix 32 is closelycoiled and has its adjacent turns welded to one another at suitablyspaced points along the inner and outer surfaces of the helix and theeffective length of this helix along its tubular axis is one-half thesonic wave length at the operating frequency. Longitudinally extendingmetal struts 34 and 36 are welded to diametrically opposite sides of theinner, face of the helix and the ends of these struts are provided withcircular flanges against which two pairs of thin metal shear plates 38and 40 are disposed, the plates being separated by compression washers42 and 44. Nuts 45 and 46 carried by the threaded ends of the strutshold the shear plates and washer assemblies tightly to the ends of thestruts.

The centers of the shear plates are separated by large compressionwashers 48 and 50 which are circumposed about the tubes 10 and 20 andthese compression washers are bolted to the flanged ends of thecouplings 12 and 22. Although the natural frequency of the helixassembly and the torsional stiffness of the tube assemblies are to someextent under the designers control, the stiffness is likely to be ratherhigh, necessitating the addition of an excess moment of inertia over andabove that which is inherent in the helix assembly, and in order toachieve this a split flywheel 52 is clamped about the hub 26 so that thenatural frequency of the helix assembly is equal to the drivingfrequency of the vibrator.

The vibrators are preferably of the electrodynamic type Where relativelyhigh frequencies are used, and as shown in Fig. 6, the vibratorcomprises a pair of rectilinear electrodynamic vibration motors 55 and56 which are rigidly secured to the supporting frame .(not shown), thesemotors having the general construction shown in my copending applicationSerial No. 553,015, filed December 14, 1955. The armature coils 58 and60 of the motors are electrically connected to produce equal andopposite forces which are transmitted tangentially to the lower end ofthe helix assembly by flexible drive links 62 and 64. These links are sodesigned that they are rigid in their axial direction, but somewhatresilient in transverse bending so as to allow for slight misalignmentof the vibration motors relative to the helix assembly. The forcesproduced by the vibration motors constitute a couple, or pure torque,which causes the helix assembly to undergo a torsional oscillation aboutits own axis.

connected with the three-phase hydraulic rectifier whichis preferably ofthe type shown in my copending application Serial No. 636,597, filedJanuary 28, 1957, now abandoned. Such a hydraulic rectifier isschematically repre'-. sented by three pairs of check valves, using theelectrical symbols, and one check valve of each pair is connected to theintake line 70 and the other to the discharge line 72.

The operation is as described in my aforementioned copending applicationSerial Nos. 553,015 and 636,597,. and combines the three advantages,namely, a half-sonicwave-length accelerator tube, a short hydrauliclength of flexible tube at each end, and a comparatively large length ofmechanically twisted tube. A further advantage is that the constructionis such as to be self-purging of trapped and entrained gases.

In Fig.9 I have shown a single unit pump designed to operate atfrequencies up to approximately 30 cycles per second and although it ishere shown as being oper-' ated by electrodynamic vibrators, it is to beunderstood that any other mechanism may be used to produce the desiredoperating frequency. Except for the telescopic torsional tubes whichhave been replaced by the hydraulic rectifiers and flexible connectinghoses, the operating parts are identical to those of unit shown in Figs.5 to 7. Accordingly, the same reference characters designatecorresponding parts.

In this embodiment the upper end of the coupling 12 is connected with arigid pipe 80 and the lower end of thecoupling 22 is connected with arigid pipe 82. These pipes fit within the inner races of .ball bearings84 and 85 which are bolted to the inner horizontalframe mern hers 86 and87. 'Mounted Within the space between the inner and outer horizontalframe members 86 and 88 is a rectifying .unit 90 comprising a housing 91having. a horizontal partition 92 and a vertical partition 93 defin-iing the chambers .94, 95 and 96 The pipe 80 is ceng nected with thechamber 96 which-in turn is connected with the chambers 94 and 95, therebeing spring-loaded ball checks 97 and 98 secured to the horizontalpartition 92. The undamped natural frequency of the check?spring-and-ball assemblies is at least twice the frequency of thevelocity variation of the propellant liquid in the. accelerator tube 32,as explained more fully in my copending application Serial No. 636,597.The ball check 97 permits liquid surges to pass only from the chamber 96into the chamber 95 and the ball check 98 permits liquid surges to passonly from chamber 94 to chamber 96. The chambers 94 and 95 are separatedby the partition 93 and thesechambers have ports 100 and 101 which arerespectively connected to heavy fatigue-resistv ing flexible tubes 102and 103 which may be of rubber or other suitable material.

Mounted within the space between the inner frame member 87 and the outerframe member 105 is another rectifying unit 90a identical with the unit90 to which similar reference characters are applied to correspondingparts. The heavy flexible tubes 102a and 103a, as well as the tubes 102and 103, are connected with the exterior circuit, as schematically shownin Fig. 10, wherein thetubes 102 and 10311 are connected to the deliveryduct 105 which runs to the receiver 106, and the tubes 103 and 102a areconnected with the return line 108.

. In operation the amplitude of the torsional movement of the helix 32is much greater than in the previously described embodiment and this ispermitted because of the flexible tubes 102, 102a, 103 and 103a, theinner ends of which oscillate in an arcuate path while their outer endsremain fixed to the frame members 88 and 105.- In all other materialparticulars the operation is as set forth in my aforementioned copendingapplications. 'Because the torsional stiffness of the flexible tubes102, 10'2a,f- 103 and 103a is likely to be rather low, it may be unnecessary to use the flywheel 52. In fact, it may be. necessary to addmore torsional stiffness in order to 1 1 make the natural frequency ofthe unit equal to the driving frequency.

It is to be understood that this disclosure is for the purpose ofillustration and that various changes and modifications may be madewithout departing from the spirit and scope of the invention as setforth in the appended claims.

I claim:

1. A pump comprising a generally annular member having end portions andproviding an accelerator tube containing a propellant liquid, means forimparting to said accelerator tube a rotary oscillatory movement so asto produce an alternating flow therein, the length of said tube beingapproximately one-half an odd integer multiple of the wave length ofsound within the liquid in the tube at the fundamental operatingfrequency, ducts connected with the end portions of said acceleratortube so as to provide an inlet and a discharge, a rectifier meansconnected with said ducts so that aunidirectional flow is produced insaiddischarge in response to an alternating flow in said acceleratortube.

2. A pumping unit comprising an accelerator tube containing a liquid,means for vibrating said tube at a predetermined frequency so as toproduce an oscillating liquid flow therein, said tube beingsubstantially nondeformable in the direction extending along its longi-.tudinal axis, the length of said tube and thus the liquid columncontained therein being approximately one half an odd integer multipleof the wave length of sound. within the liquid in the tube at thefundamental operating frequency, and hydraulic rectifying meansconnected with, said tube so that a unidirectional. dischargeis producedin response to an oscillating flow in said tube;

3. A pumping unit comprising. a coiled accelerator tube containing aliquid, means for impartinga rotary oscillatory movement ofpredetermined frequency to said tube so as to produce an oscillatingliquid flow therein, the axial length of said tube being approximatelyone half an odd integer multiple of the wave length of soundwithin theliquid in the tube at the fundamental operating frequency, and hydraulicrectifying means connected with said tube so that a unidirectionaldischarge is produced in response to an oscillating flow in said tube.

4. A pumping unit comprising an accelerator tube containing a liquid,means for vibrating said tube at a frequency of at least twenty cyclesper second so as to produce an oscillating liquid flow. therein, saidtube being substantially non-deformable in the direction extending alongits longitudinal axis, the length of said tube and thus the liquidcolumn contained therein being approximately one half the wave length ofsound within the. liquid in the tube at the fundamental operating,frequency, and hydraulic rectifying means connected with said tube sothat a unidirectional discharge is produced in response to anoscillating flow in said tube.

5. A pumping unit comprising a coiled accelerator tube containing aliquid, means for imparting a rotary oscillating movement of at leasttwenty cycles per second to said tube so as to produce an oscillatingliquid flow therein, the axial length of said tube being approximatelyone half the wave length of sound within the liquid in the tube at thefundamental operating frequency, and hydraulic rectifying meansconnectedwith said tube so that a unidirectional discharge isproduced in responseto an oscillating flow in said tube.

6. In a pumping system adapted to be connected} with an exterior circuithaving a delivery line and a return line, a pump unit comprising anaccelerator tube containing a liquid, means for vibrating saidtube atapredetermined frequency so as toproduce an oscillating liquid flowtherein, said tube being substantially non-deformable in the directionextending along its longitudinal axis, the lengthof saidrtube andthusthe liquidcolumn -contained therein being approximately one half anodd'in t'eger multiplev of the wave length of sound. within the liquidin the tube at the fundamental operating frequency, and hydraulicrectifier means connected with said tube and with the delivery andreturn lines so that a unidirectional flow takes place in the deliveryline in response to an oscillating flow in said tube;

7. In a pumping system adapted tobe connected with an exterior circuithaving a delivery line and a return line, a pump unit comprising ahelical accelerator tube containing a liquid, means for imparting tosaid tube a rotary oscillatory movement of predetermined frequency so asto produce an oscillating liquid flow therein, the length of said tubebeing approximately one half an odd integer multiple of the wave lengthof sound within the liquid in the tube at the fundamental operatingfrequency, and hydraulic rectifier means connected with said tube andwith the delivery and return lines so that a unidirectional flow takesplace in the delivery line in response to an oscillating flow in saidtube.

8. A pump unit comprising a helical accelerator tube containing aliquid, a cylindrical supporting member coaxial with said tube, couplingmeans at the opposite ends of said supporting member, means connectingthe opposite ends of saidtube with said coupling means, means forimparting a rotary oscillatory movement of predetermined frequency tosaid tube so as to produce an oscillating liquid flow therein, the axiallength of said tube being approximately one half an odd integer multipleof the wave length of sound within the liquid in the tubeat thefundamental operating frequency, and hydraulic rectifier means connectedwith said coupling means so that a unidirectional discharge is producedin response to an oscillating flow in said tube.

9. A pump unit comprising a helical accelerator tube containing aliquid, a cylindrical supporting member coaxial with said tube, couplingmeans at the opposite ends of said supporting member, meansconnectingthe opposite ends of said tube with said coupling means, meansfor imparting a rotary oscillatory movement of predetermined frequencyto said tube so as'to produce an oscillating liquid flow therein, theaxial length of said tube being approximately one half an odd integermultiple of the wave length of'sound within the liquid in the tube atthe fundamental operating frequency, a flywheel secured to saidsupporting member between said coupling means. and hydraulic rectifiermeans connected with said coupling means so that aunidirectionaldischarge isiproduced in.

response to an oscillating flow in said tube.

10. A pump as set forth in claim- 9, wherein said flywheel is soconstructed' that its moment of inertia can be varied.

11. A pump unit comprising a helical accelerator tube containing aliquid, a cylindrical supportingmember coaxial with said tube, couplingmeans secured to the opposite ends of said supporting member, meansconnecting the opposite ends of said tube with said coupling means,means for imparting a rotary oscillatory movement of predeterminedfrequency to said tube so as to produce an oscillating liquid flowtherein, the axial length of said tube being approximately one half anodd integer multiple of the wave length of sound within the liquid inthe, tube at the fundamental operating frequency, flexible tubesconnected with said coupling means, said flexible tubes being capable ofundergoing a torsional movement,

a rotary oscillatory movement of predetermined fre quency so as toproduce an oscillating liquid flow in said 13 tube, the axial length ofsaid tube being approximately one half an odd integer multiple of thewave length of sound within the liquid in the tube at the fundamentaloperating frequency, and hydraulic rectifier means connected with saidtube so that a unidirectional discharge is produced in response to anoscillating flow in said tube.

13. A pump unit comprising a helical accelerator tube containing aliquid, means for imparting a rotary oscillatory movement ofpredetermined frequency to said tube so as to produce an oscillatingliquid flow therein, the axial length of said tube being approximatelyone half an odd integer multiple of the wave length of sound within theliquid in the tube at the fundamental operating frequency, and a torsiontube assembly including a plurality of spaced telescopically disposedtubes having interconnected end portions, said torsion tube assemblybeing connected at one end with one end of said accelerator tube andhaving means at its other end for rigidly mounting said other end to aframe and the like.

14. A pump unit comprising a helical accelerator tube containing aliquid, means for imparting a rotary oscillatory movement ofpredetermined frequency to said tube so as to produce an oscillatingliquid flow therein, the axial length of said tube being approximatelyone half an odd integer multiple of the wave length of sound within theliquid in the tube at the fundamental operating frequency, and a pair oftorsion tube assemblies each including a plurality of spacedtelescopically disposed torsion tubes having interconnected ends, saidpair of torsion tube assemblies being respectively connected at one endwith the opposite ends of said accelerator tube and having means attheir other ends for rigidly mounting said other ends to a frame and thelike.

15. A pump unit comprising a helical accelerator tube containing aliquid, a cylindrical supporting member coaxial with said tube, couplingmembers at the opposite ends of said supporting member, means connectingthe opposite ends of said tube with said coupling members, means forimparting a rotary oscillatory movement of predetermined frequency tosaid tube so as to produce an oscillating liquid flow therein, the axiallength of said accelerator tube being approximately one half an oddinteger multiple of the wave length of sound Within the liquid in thetube at the fundamental operating frequency, and a pair of torsion tubeassemblies each including a plurality of spaced telescopically disposedtorsion tubes having interconnected ends, said assemblies beingrespectively connected at one end with said coupling members and havingmeans on their other ends for rigidly mounting said other ends to aframe and the like.

16. A pump as set forth in claim 15 wherein a flywheel is mounted onsaid cylindrical supporting member between said coupling members.

17. A pump unit comprising a helical accelerator tube containing aliquid, a cylindrical supporting member coaxial with said tube, couplingmembers at the opposite ends of said supporting member, means connectingthe opposite ends of said tube with said coupling members, means forimparting a rotary oscillatory movement of predetermined frequency tosaid tube so as to produce an oscillating liquid flow therein, the axiallength of said accelerator tube being approximately one half an oddinteger multiple of the wave length of sound within the liquid in thetube at the fundamental operating frequency, hydraulic rectifiersconnected with said coupling members, said rectifiers having intake anddischarge ports, and interconnected flexible tubes connected with theintake and discharge ports so that a unidirectional flow is produced insaid discharge ports in response to an oscillating flow in saidaccelerator tube.

18. A pump comprising a generally annular member having end portions andproviding an accelerator tube containing a propellant liquid, means forimparting to said accelerator tube a rotary oscillatory movement so asto produce an alternating flow therein, the length of said tube beingapproximately one-half an odd integer multiple of the wave length ofsound within the liquid in the tube at the fundamental operatingfrequency, coaxial ducts connected with the end portions of saidaccelerator tube so as to provide an inlet and a discharge, andrectifier means connected with said ducts so that a unidirectional flowis produced in said discharge in response to an alternating flow in saidaccelerator tube.

19. A pump comprising a generally annular member providing anaccelerator tube having a pair of ends and containing a propellantliquid, means for imparting to said accelerator tube a rotaryoscillatory movement so as to produce an alternating flow therein, aduct capable of undergoing torsional oscillatory movement connected toone end of said tube, and rectifier means interposed between said ductand the end of said accelerator tube, said rectifier means having intakeand discharge ports and check valves operative to produce aunidirectional flow through the discharge port in response to analternating flow in said accelerator tube.

20. A pump comprising a generally annular member having end portions andproviding an accelerator tube containing a propellant liquid, means forimparting to said accelerator tube a rotary oscillatory movement so asto produce an alternating flow therein, inlet and discharge ductsconnected with the end portions of said accelerator tube, said ductsbeing coaxial with said accelerator tube and with each other, at leastone of said ducts being capable of undergoing torsional oscillatorymovement, and rectifier means connected with said ducts so that aunidirectional flow is produced in said discharge duct in response to analternating flow in said accelerator tube.

References Cited in the file of this patent UNITED STATES PATENTS 89,390Dumont Apr. 27, 1869 391,189 Pontallie Oct. 16, 1888 1,745,979 CalvertFeb. 4, 1930 2,444,912 Bodine July 13, 1948 2,643,816 Lewis June 30,1953 FOREIGN PATENTS 106,989 Great Britain June 7, 1917 130,332 GreatBritain July 29, 1920

